Module 3 – Exchange and transport Flashcards
(126 cards)
1
Q
C7) What are the 2 reasons why diffusion alone is enough to supply the needs of single celled organisms
A
the metabolic activity of it is usually low, so the o2 demand and co2 production is low
the SA:V ratio of it is large
2
Q
C7) why is SA:V ratio important in exchange surfaces
A
Because the bigger the organism the smaller the SA:V ratio
Important because the distances the substances have to travel from the outside to reach the cell at the centre of the body gets longer .
therefore it make it harder to absorb enough o2 through the available SA to meet the need
3
Q
C7) what are the key features of effective exchange surface
A
increased SA: provides the area needed for exchange and overcome limitations of Small SA:V ratio ( villi in the small intestine)
Thin layers: means the distance that substances have to diffuse are short making it fast and efficient. (alveoli in the lungs)
Good blood supply: the steeper the concentration gradient the faster the diffusion. This ensures substances are constantly delivered to and removed from the exchange surface. allows a steep concentration gradient. (gills of a fish)
Ventilation to maintain diffusion gradient: for gases this helps maintain concentration gradient and make it more efficient
4
Q
C7) what are the key features of the nasal cavity
A
a large SA with a good blood supply which warms the air to body temperature
A hairy lining which secretes mucus to trap dust and bacteria protecting long tissue from irritation and infection
Moist surface, which increases the humidity of the incoming air, reducing evaporation from the exchange surface
The air enters the lungs is at a similar temperature and humidity to hear
5
Q
C7) What are the key features of the trachea
A
Is the main airway carrying clean, warm and moist air from the nose into the chest
A wide tube supported by incomplete rings of strong, flexible cartilage which stops the trachea from collapsing. Incomplete rings to allow food to move easily down the oesophagus beside the trachea
It and its branches are lined with ciliated epithelium with goblet cells between and below the epithelial cells.
Goblet cells secrete mucus into the lining of the trachea to trap dust and microorganisms that have escaped the nose lining
The cilia beat and move the mucus along with any trapped dust and microorganisms away from the lungs this is known as locomotion. It goes into the throat and is swallowed and Digested
6
Q
C7) What are the key features of the Bronchus
A
Plural is bronchi
Right bronchus = right lung
Left bronchus = left lung
Similar structures to the trachea
With some supporting rings of cartilage but they are smaller
7
Q
C7) What are the features of the bronchioles
A
The bronchi divide to form these
Smaller bronchioles have no cartilage rings
The Bronchioles contain smooth muscle
When the smooth muscle contracts the bronchioles construct (close up). When it relaxes the bronchials dilate (open up). This changes the amount of air reaching the lungs
They are lined with a thin layer of flattened epithelium making some gases exchange possible.
8
Q
C7) What are the features of the alveoli
A
Has a diameter of around 200 to 300 um
Consist of a layer of thin flattened epithelium cells with some cartilage and elastic fibres
Elastic tissue allows the alveoli to stretch as air is drawn in. When they return to their resting size they help squeeze the air out. This is known as elastic recoil of the lungs
9
Q
C7) What are the main adaptation of the alveoli for effective gaseous exchange
A
Large surface area - there are 300 to 500 million alveoli per adult lung.
Thin layers - both the alveoli and capillaries that surround them have walls that are a single epithelium cells thick. So the diffusion distance between the air in the alveoli and the blood in the capillaries are short
Good blood supply - The millions of alveoli in each long are surrounded by a network of around 280 million capillaries. The constant flow of blood through these capillaries brings carbon dioxide and carries of oxygen maintaining a steep concentration gradient
Good ventilation - breathing moves air in and out of the alveoli, helping maintain steep diffusion gradient of oxygen and carbon dioxide
10
Q
C7) what is ventilation
A
It is moved in and out of the lungs as a result of pressure change in the thorax brought about by the breathing movement
11
Q
C7) How does inspiration work
A
This is an energy use processed
The diaphragm contracts, flattening and lowering
The external intercostal muscle contracts moving the ribs upwards and outwards
The volume of the thorax increases so the pressure in the thorax is reduced
It is now lower than the pressure of the atmospheric air so it is shown through the nasal passages, trachea, bronchi and bronchioles into the lungs
This equalise the pressure inside and outside the chest
12
Q
C7) how does expiration work
A
Normal expiration is a passive process
The diaphragm relaxes so it moves up into its resting dome shape
The external intercostal muscle relaxes so the ribs move down and inwards under gravity
The elastic fibres in the alveoli of the lungs are returning to their normal lengths
These changes decrease the volume of the thorax, the pressure inside the thorax is greater than the pressure of the atmospheric air
So the air moves out of the lungs until the pressure inside and outside is equal again
If you exhale forcefully it uses energy.
The internal intercostal muscle contracts pulling the ribs down hard and fast and the abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly
13
Q
C7) What are all the variety of different ways to measure the capacity of the lung
A
A peak flow meter- A simple device that measures the rate at which they can be expelled from the lungs. Used by people with asthma to Monitor the longs
Vitalograph- more sophisticated version of the peak flow meter. The patient breathe out as quickly as possible thorough A mouthpiece and the instrument produces the graph of the amount of air they breathed out and how quickly it is breathed out this is called the forced expiratory volume in one second
Spirometer- used to measure different aspects of the lung volume or to investigate breathing patterns.
14
Q
C7) what is tidal volume
A
The volume of air that moves into and out of the lungs with each resting breath. Around 500 cm³ in most adults at rest using about 15% of the vital capacity of the lung
15
Q
C7) what is vital capacity
A
The volume of air that can be breathe in when the strongest possible exhalation is followed by the deepest possible intake of breath
16
Q
C7) what is inspiratory reserve volume
A
Is the maximum volume of a air you can breathe in over and above a normal inhalation
17
Q
C7) What is expiratory reserve volume
A
The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
18
Q
C7) What is residual volume
A
The volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly
19
Q
C7) what is total lung capacity
A
The sum of the vital capacity and the residual volume
20
Q
C7) what is the breathing rate
A
Number of breaths taken per minute
21
Q
C7) what is the ventilation rate
A
The total volume of air Inhaled in one minute
22
Q
C7) what is the equation for ventilation rate
A
Ventilation rate = tidal volume * breathing rate per minute
23
Q
C7) what is the gassiest exchange system of an insect
A
They deliver oxygen directly to the cells and to remove the carbon dioxide in the same way this is because of the tough exoskeleton which does not allow for gases exchange and they do not have blood pigments that carry oxygen
24
Q
C7) how does gassiest exchange to take place in Insects
A
Insects have a small opening along the thorax and abdomen called spiracles.
Enters and leaves the system through spiracle but water is also
the spiracles can be opened or closed by sphincters. The sphincters keep the spiracles closed as much as possible to minimise water loss.
When an insect is an active and oxygen demand is low this particles are closed, when oxygen demand is rising all the carbon dioxide level is building up the spare keys are open
After the spiracles it is the tracheae(Large tubes of the insect respiratory system) and they carry it into the body. Lined with spirals of chitin keeping them open when bent or pressed. Trachea impossible for gases exchange as it is impermeable to gases
After the tracheae it branches into the tracheoles which are smaller. A single largely elongated cell with no chitin so are permeable to gases. Because they are small they spread throughout the tissue running between individual cells where gases exchange can happens
Most insects air moves along the system by diffusion alone and reaching all the tissue
Towards the end of the tracheoles there is trickier fluid which limits the penetration of air for diffusion into the cells
When oxygen demand builds up,a lactic acid build up in the tissue result in water moving out of the tracheoles by diffusion
25
C7) what are the alternative methods of increasing the levels of gases exchange for insects with very high energy demands
Mechanical ventilation of the Tracheal system -
air actively pumped into the system by muscular pumping movement of the thorax and the abdomen.
This movement changes the volume of the body and this changes the pressure within the system so air is drawn in or out
Collapsible enlarged tracheae or air sack that act as a reservoirs -
used to increase the amount of air through the gases exchange system.
Usually inflated and deflated by the ventilating movement of the thorax and abdomen
26
C7) What are the difficulties that the respiratory system of fishes need to overcome
The water is more dense,viscous and it has a much lower oxygen content compared to air
It would use up too much energy to move dents, viscous water in and out of a lung like respiratory organ, therefore moving water in One Direction only is much simpler and saves more energy
27
C7) how does the gills help with effective gases exchange in fish
Because fish are very active their cells have a high demand of oxygen. The SA:V ratio means that diffusion would not be enough to supply oxygen to the cells and the scalae covering the does not allow gaes exchange
Adapt to a system to take oxygen from water and get rid of carbon dioxide into the water. Maintain a flow of water in One Direction over the gills which are their gassiest exchange organ.
Gilles have a large surface area, Good blood supply and thin layers needed for successful gases exchange. They are contained in a Gill cavity and covered by a protective operculum, also active in maintaining a flow of water over the gills
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C7) How does water move over the gills
When fish are swimming they can keep a current of water flowing over the gills simply by opening their mouth and a operculum so when they stop the water flow stops.
So most fish do not rely on movement generated water flow over the gills
The mouth opens and the floor of the buccal cavity lowers. Increasing the volume of the buccal cavity resulting in a decrease in pressure in the cavity moving water into the cavity.
At the same time the operculum shuts and the operculum cavity containing the gills expand lowering the pressure in the operculum cavity containing the gills.
The buccal cavity starts to move up increasing the pressure so water moves from the buccal cavity over the gills
The mouth closes, the operculum Opens and the sides of the operculum cavity moves inwards therefore increasing the pressure in that particular cavity and water is forced out over the gills through operculum The floor of the buccal cavity is moved upwards
29
C7) How are the gills effective gases exchange in the water
Have a large surface area for diffusion
A rich blood supply to maintain steep concentration gradient
Thin layers for short diffusion pathway
The tips of adjacent Gill filaments overlap - increases the resistance to the flow of water over the gills surface and slows down the movement of water increasing time for gases exchange
The water moving over the gills and the blood in the girl filaments flow in different directions. Steep concentration gradient is needed. As water and blood flow in different directions account the current exchange system is set up to get the steep concentration gradient
30
C7) what is ram Ventilation
When cartilaginous fish often rely on continuous movement to ventilate the gills
They just ram the water past the gills
31
C8) why do multi cellular organisms need a specialised transport system
The metabolic demand of most multicellular animals are high. So diffusion over the long distance is not enough to supply the need
The surface area to volume ratio gets smaller as multi cellular organisms get bigger so not only do the diffusion distance get bigger but the amount of surface area available for diffusion get smaller
Molecules such as hormones and enzymes may be made in one place but needed in another
Food will be digested in one organ system but needs to be transported to every cell for use in respiration
Waste products of metabolism Need to be removed from the cells and transported to excretory organs
32
C8) what is the need for a transportation system
To supply oxygen and nutrients to the sites where they are needed and to remove waste products from the individual cells
33
C8) what features do most circulatory systems have in common
They have a liquid transport medium that circulates around the system
They have vessels that carry the transport medium
They have a pumping mechanism to move the fluid around the system
34
C8) what is a mast transport system
When substances are transported in a mass of a fluid with a mechanism to move the fluid around the body
35
C8) what is an open circulatory system
There are very few vessels to contain the transporter medium
Pump straight from the heart into the body cavity of the animal
The open body cavity is called the haemocoel, Here the transport medium is at low pressure so it comes into direct contact with tissues and cells, where exchange takes place. The transport medium returns to the heart through an open ended vessel
36
C8) where are open ended circulatory system is mainly found
In invertebrate animals including insects
Insect blood is called haemolymph. It does not carry oxygen or carbon dioxide. It transports food and nitrogenous waste products and the cells involved in defence against disease
The haemolymph circulates but steep diffusion gradient cannot be maintained for affective diffusion. Amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demand
37
C8) what is a closed circulatory system
Blood is included in blood vessels and does not come directly in contact with the cells of the body
Heart pumps blood around the body under pressure and relatively quickly and the blood returns directly to the heart
Substances leave and into the blood by diffusion through the walls of the blood vessel
The amount of blood flowing to a tissue can be adjusted by narrowing and widening the blood vessels
Most closed circulatory systems contain blood pigments that carry the respiratory grasses
38
C8) what is a single closed circulatory system
The blood travels only once through the heart for each complete circulation of the body
The blood passes through two sets of capillaries before he returns to the heart.In the first set of capillary it exchanges oxygen and carbon dioxide. In the second set of capillary The substance is exchanged between blood and the cells
As a result of very narrow vessels the blood pressure drops considerably so the blood returns to the heart slowly therefore limiting the exchange process so the animals activity levels are relatively low
39
C8) why does a fishes single closed circulatory system work effectively
Because they have a counter current gassiest exchange mechanism which allows take up of a lot of oxygen. Their body weight is supported by water and they do not maintain their own body temperature therefore reducing the metabolic demand on their bodies
40
C8) What is a double closed circulatory system
Mammals and birds are very active and maintain their own body temperature made possible by the double closed circulatory system
Most effective system for transporting substances around the body
The blood travels twice through the heart in a circuit of the body. Each circuit - to the lungs and to the body only passing through one capillary network so a relatively high pressure and fast flow of blood
41
C8) what are the two separate circulation in the double closed circulatory system
Blood is pumped from the heart to the lungs to pick up oxygen and on load the carbon dioxide and then returns to the heart
Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
42
C8) what are the different components utilised in some blood vessels
Elastic fibres - composed of elastin and can stretch and recoil providing vessel walls with flexibility
Smooth-muscle- contracts or relaxes, which changes the size of the lumen
Collagen-provide structural support to maintain the shape and volume of the vessel
43
C8) when are the times an artery does not Carrie oxygenated blood
The pulmonary artery which carries deoxygenated blood to the lungs
During pregnancy the umbilical artery carries deoxygenated blood from the fetus to the placenta
44
C8) what are the structural components of arteries and arterioles
Artery walls contain elastic fibre, smooth-muscle and collagen.
Elastic fibre enables them to withstand the force of the blood pumped out of the heart and stretch to take the large volume of blood
Between contractions of the heart elastic fibres recoil and return to their original length helping to even out the surge of blood pumped from the heart for a continuous flow. The elastic fibre cannot completely eliminate the surge of blood giving a pulse
The endothelium is smooth so blood can flow easily
Arterioles have more smooth-muscle and less elastin in their walls as they have little pulse surges but can contract and dilate to control the flow of blood
45
C8) what is the meaning of Vasoconstriction
The smooth-muscle in the arterial contract, constricts the vessel and prevent blood flowing into a capillary bed
46
C8) What is the meaning of Vasodilation
When the smooth-muscle in the walls of the arterial relax, blood flow through into the capillary bed
47
C8) how are the capillaries adapted to their role in the circulatory system
Provide a very large surface area for the diffusion of substances in and out of the blood
The walls are a single endothelium cell thick for a short diffusion pathway
The cross-sectional area of the capillaries is greater than the arterial supplying so the rate of bloodflow falls. Slow movement of blood through capillaries gives more time for exchange of materials by diffusion
48
C8)What are the exceptions of veins carry deoxygenated blood
Pulmonary vein carries oxygenated blood from the lungs to the heart
Umbilical vein carries oxygenated blood from the placenta to the fetus
49
C8) what are the structural components of Venules and veins
Venues have very thin walls with little smooth-muscle several venules join to form A vein
Veins do not have a pulse-the surge of blood from the heart pumping is lost in the narrow capillaries.
Veins hold a large reservoir of blood
The blood pressure in the veins is very low compared to the pressure in the arteries so they have valves to prevent back flow of blood
Walls contain loads of collagen and little elastic fibre, and the vessel has a wide lomen and a smooth, thin endothelium so blood flows easily
50
C8) What are the main adaptations to enable the body to move blood against gravity in a vein
The majority of veins have valves at intervals. These are flaps of the inner lining of the vein. When blood flows in the direction of the heart the valves open so the blood passes through but if the Blood starts to flow backwards the valves closed to prevent this from happening
Many of the bigger veins run between the big active muscles in the body for example the arms and legs. When the muscle contracts they squeeze the veins forcing the blood upwards towards the heart. Valves prevent back flow when muscle is relaxed
The breathing movement makes the chest acts like a pump. The pressure changes and the squeezing action moves blood in the veins of the chest and abdomen towards the heart
51
C8) What is blood plasma made of
Yellow liquid which carries a wide variety of other components including dissolved glucose and amino acids, mineral ions, hormones and large plasma proteins.
Also transports red blood cells (Erythrocytes) and the many different types of white blood cells (leucocytes)
Also carries platelets (thrombocytes) which are fragments of large cells called megakaryocytes found in the blood bone marrow which are involved in the clotting mechanism of blood
52
C8) What is the function of blood as a transport medium
To transport:
oxygen to, and carbon dioxide from, the respiring cells
Nitrogenous waste products from the cells to the excretory organ
Chemical Messages
Food molecules from storage compartments to the cells that need them
Platelets to damaged areas
Also contributes to maintain a steady body temperature and act as a buffer maintaining pH
Cells and antibodies involved in immune response
53
C8) How is oncotic pressure created
The substances dissolved in plasma can pass through fenestrations in the capillary walls except large plasma proteins eg albumin
The large plasma proteins have an oncotic effect by giving the blood in the capillaries a relatively high solute potential and a low water potential compared to the surrounding fluid
As a result water tends to move into the blood in the capillaries from the surrounding fluid by osmosis this is known as oncotic pressure
54
C8) How is tissue fluid created
As blood flows through the arterioles into the capillaries it is under pressure from the surge of blood that occurs as a result of heart contractions this is known as hydrostatic pressure
At the arterial end of the capillary hydrostatic pressure forcing fluid out of the capillaries is relatively higher than the oncotic pressure attracting water in by osmosis
So fluid is squeezed out of the capillaries, the fluid fills the spaces between the cells is called tissue fluid.
As the blood moves through the capillaries towards the Venuses end. The hydrostatic pressure falls in the vessels as fluid has moved out and the pulse is completely lost. As the oncotic pressure remains the same and is stronger than the hydrostatic pressure, water moves into the capillaries by osmosis
90% of the tissue fluid is back in the land parcel at the end of the vein
55
C8) what is the composition of tissue fluid
Same composition as plasma without the red blood cells and plasma protein
Diffusion takes place between the blood and the cells through the tissue fluid
56
C8) how does the lymphatic system work
Some of the tissue fluid that does not return to the capillaries. 10% of the liquid that leaves the blood vessel drains into a system of blind ended tubes called lymph capillaries where it is known as lymph
Length is similar in composition to plasma and and tissue fluid but has less oxygen and fewer nutrients. Also contains fatty acids which have been absorbed into the lymph by the villi in the small intestine
Fluid is transported through lymph capillaries joining up to form large vessels by the squeezing of body muscles
They have one-way valves
The length of returns to the blood flowing through the right and left subclavian veins
57
C8) What are lymph-nodes
along lymph vessels
Lymphocytes build up in the lymph nodes when necessary and produce antibodies which then pass into the blood
Lymph-node’s intercept bacteria and debris from the lymph which was ingested by phagocytes found in the node
Lymphatic system plays a major role in defence mechanisms in the body
Enlarged lymph nodes are signs that the body is fighting off and invading pathogen. This is why doctors examine the neck, armpits and stomach which are sites of some of the major lymph-nodes
58
C8) how are Erythrocytes specialised transport oxygen
Have a biconcave shape-large surface area therefore allowing for more diffusion of gases also allowing them to pass through narrow capillaries
Formed continuously in bone marrow
They have no nuclei which maximises the amount of haemoglobin that fits into the cell, also limits their life
Contain haemoglobin which carries oxygen. Haemoglobin is a very large globular protein made up of four peptide chains each with a heam prosynthetic group
The making of Oxyhaemoglobin is a reversible reaction
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C8) How do Erythrocytes carry oxygen
Erythrocytes into the capillaries in the lungs oxygen level in the cell is relatively low allowing for a steep concentration gradient between the inside of the Erythrocytes and the air in the alveoli
Oxygen moves in and binds to the haemoglobin.
Arrangement of the haemoglobin molecule means that as soon as one oxygen molecule binds to haem group, The molecule changes shape making it easier for the next oxygen to bind this is called positive cooperativity. Because the oxygen is bound to the haemoglobin, the free oxygen concentration in Erythrocytes stays low therefore a steep concentration gradient until all the haemoglobin is saturated with oxygen
When the blood reaches the body tissue the concentration of oxygen in the celles is lower than in the Erythrocytes so the oxygen will move down the concentration gradient towards the cells.
Once the first oxygen molecule is released by the haemoglobin the molecule again change the shape and it becomes easier to remove the remaining oxygen molecules
60
C8) How does an oxygen dissociation curve help to understand how haemoglobin carries oxygen
It shows the affinity for oxygen by haemoglobin
A very small change in partial pressure of oxygen in the surroundings and make a significant difference to the saturation of haemoglobin because of positive cooperative when one oxygen binds to a hem group, changes the shape of haemoglobin to allow more oxygen to bind
The curve levels out at the highest partial pressure of oxygen because all the hame groups are bound to oxygen and cannot take anymore
This means that the high partial pressure of oxygen in the lungs haemoglobin is rapidly loaded with oxygen. On the other hand a relatively low partial pressure in the tissue rapidly unload the oxygen from haemoglobin
61
C8) what is the Bohr effect
As the partial pressure of carbon dioxide rises haemoglobin gives up oxygen more easily
62
C8)What is the importance of the Bohr effect in the body
In active tissue with a high partial pressure of carbon dioxide haemoglobin gives up its oxygen more easily
In the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily
Curve moves to the right
63
C8) what is the importance of fetal haemoglobin
Oxygenated blood from the mother runs close to the deoxygenated fetal blood in the placenta
If the blood of the fetus has the same affinity for oxygen as the blood of the mother then little or no oxygen would be transferred to the blood of the fetus
Fetal haemoglobin has a higher affinity for oxygen the adult haemoglobin. So it removes oxygen from the maternal blood as they move past each other
Curve moved to the left
64
C8) what is the different ways in which carbon dioxide is transported from the tissues to the lungs
5% is carried dissolved in the blood plasma
10 - 20% is combined with the amino groups in the polypeptide chain of haemoglobin to form a compound called Carbaminohaemoglobin
75 - 85% is converted into hydrogen carbonate ions in the cytoplasm of the red blood cell
65
C8) how does carbon dioxide get transported in Red blood cells from tissue to the lungs
Carbon dioxide reacts slowly with water to form carbonic acid (H2CO3-). The carbonic acid then dissolves to form hydrogen ions and hydrogen carbonate ions
In the blood plasma this reaction happens slowly. However in the cytoplasm of the red blood cell there are large levels of the enzyme carbonic anhydrase.
Which catalyse the reversible reaction between carbon dioxide and water to form carbonic acid. The carbonic acid then dissolves to form hydrogen carbonate ions (HCO3-) and hydrogen ions (H+)
Negatively charged hydrogen carbonate ions move out of the Erythrocytes into the blood plasma by diffusion and negatively charged chloride ions move into the Erythrocytes to Maintaining the electrical balance of the cell this is known as chloride shift
Hydrogen ions are excepted by haemoglobinIn a reversible reaction to form Haemoglobinic acid. Haemoglobin acts as a buffer and prevents changes in pH
66
C8) why is it important to remove carbon dioxide and convert it into hydrogen carbonate ions in the red blood cell
Erythrocytes maintains a steep concentration gradient for carbon dioxide to diffuse from the respiring tissues into the Erythrocytes
67
C8) how does carbon dioxide leave the red blood cell to the lung tissue
In the lung tissue there is a relatively low concentration of carbon dioxide.
Carbonic anhydrase catalyses the reverse reaction breaking down carbonic acid into carbon dioxide and water
Haemoglobinic acid is reversed into hydrogen ions and haemoglobin
Hydrogen carbonate ions diffused back into Erythrocytes and react with hydrogen ions to form more carbonic acid. When carbonic acid is broken down by carbonic anhydrase it releases free carbon dioxide which diffuses out of the blood into the lungs
Chloride ions diffused out of the Red blood cell into the plasma down and electrochemical gradient
68
C8) what artery applied blood to the cardiac muscle
Coronary artery
69
C8) what is the importance of inelastic paracardial membrane
Helps to prevent the heart from over distending with blood
70
C8) What are the important structures and features of the heart
Deoxygenated blood from the upper body enters the right atrium from the superior vena cava and from the lower body in the inferior Veena Cava
Tenderness cord make sure valves are not turned inside out by the pressure excreted when the ventricles contract
Semilunar valves prevent back flow of blood into the heart
The septum is that in the dividing wall of the heart which prevents the mixing of deoxygenated and oxygenated blood
The right and left side of the heart fill and empty together
71
C8) why is the muscular wall of the left side of the heart thicker than the right
because the lungs are relatively close to the heart and the lungs are smaller than the rest of the body so the right side of the heart has to pump the blood a relatively slow distance and only has to overcome the resistance of the pulmonary circulation
The left side has to produce significant force to overcome the resistance of the aorta and the anterior systems of the whole body and move the blood under pressure to all the extremities
72
C8) What is diastole
When the heart relaxes
The atria and then the ventricles filled with blood. The volume and the pressure of blood in the heart build as the heart fills but the pressure in the arteries is at a minimum
73
C8) What is systole
The atria contract (atrial systole) Closely followed by the ventricles contracting (ventricular systole)
The pressure inside the heart increases dramatically and blood is forced out of the right side of the heart to the lungs and from the left side to the main body circulation
The volume and pressure of the blood in the heart are low at the end of systole and the temperature in the arteries is at maximum
74
C8) What are the stages of the cardiac cycle
1) The ventricles are relaxed. The atria contract which decreases the volume and increases the pressure. This pushes the blood into the ventricles through the atrioventricular valves. There is a slight increase in ventricular pressure and volume as the ventricles receive the injected blood from the contracting atria
2) The atria relax. The ventricles contract decreasing their volume, increasing The pressure. The pressure becomes higher in the ventricles than the atria which forces the atrioventricular valves to shut to prevent back flow.The higher pressure in the ventricles open the semilunar valves- blood is forced out into the pulmonary artery and aorta
3) The ventricles and the atria both relax. The higher pressure in the pulmonary artery and aorta cause the semilunar valves to close preventing backflow. The atria fill with blood increasing the pressure due to the higher pressure in the vena cava and pulmonary vein. As the ventricles continue to relax the pressure falls below the pressure of the atria causing the atrioventricular valves to open and blood flows passively into the ventricles from the atria. The atria contract and start the process again
75
C8) where does the hearts sound come from
The first sound comes from the blood being forced against the intraventricular out as the ventricles contract
The second sound comes as a back flow of blood closes the semilunar valves in the atria and pulmonary artery as the ventricles relax
76
C8) what does it mean for the heart muscle to be myorgenic
It has a own intrinsic rhythm at around 60 bpm
This prevents the body wasting resources maintaining the basic heart rate
77
C8) How is the basic rhythm of the heart maintain
A wave of electrical excitation begins at the Sino atrial node within the pacemaker area. This causes the atria to contract and so initiating a heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles
Electrical activity from The Sino atrial node is picked up by the atrioventricular node. The atrioventricular node imposes a slight delay before stimulating the bundle of his, a bundle of conducting tissue made up of purkyne fibres which penetrate through the septum between the ventricles
The bundle of his splits into two branches and conduct the wave of excitation to the apex of the heart
At the apex the purkyne fibres out through the walls of the ventricles on both side spreading the wave of excitation causing the contraction of the ventricles starting at the apex. This is to allow more efficient emptying of the ventriclesS
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C8) Why does the atrioventricular node delay occur
To make sure the atria has stopped contracting before the ventricles start
79
C8) What is considered tachycardia
When the heartbeat is very rapid over 100 bpm
Normal when exercising, having a fever, are frightened or angry
Abnormal causes may be a problem in the electrical controls of the heart and may need surgery to fix it or medication
80
C8) what is considered bradycardia
When the heart rate slows down to below 60 bpm
Many people have bradycardiac because they are fit-making the heart beat more slowly and effectively
Severe bradycardia can be serious and may need an artificial pacemaker to keep the heart beating steadily
81
C8) what is considered to be an ectopic heartbeat
An extra heartbeat that is out of the normal rhythm
Can be linked to serious conditions and they occur frequently
82
C8) what is considered to be atrial fibrillation
Example is arrhythmia, which means an abnormal right of the heart
Rapid electrical impulses are generated in the atria
They contract very fast. However they do not contract properly and only some of the impulses are passed onto the ventricles which contracts much less often therefore not pumping blood efficiently
83
C8) cardiac output
= Heart rate * sroke volume
84
C9) what are the three main reasons why multicellular plants need transport systems
Metabolic demand: The cells of the green parts of the plant make that own glucose and oxygen by photosynthesis but many internal and underground part of the plant do not photosynthesise, need oxygen and glucose transporter to them and metabolic waste products removed. For the transport of hormones to the place they take effect. Mineral ions absorb at the root need to be transported to cells to make proteins
Size: some plants are very small because plants continues to grow throughout their lives meaning plants need very efficient transport systems to move substances up and down from the tip of the route to the uppermost leaves and stem.
SA:V ratio: leaves are adapted to have a relatively large surface area to volume ratio for the exchange of gases. When taking the WholePlant into account they still have a relatively small surface area to volume ratio meaning they cannot rely on diffusion alone to supply for cellular needs
85
C9) what are dicotyledonous plants
Make seeds that contain 2 cotyledons, organs that act as food stores for the developing embryo plant and form the first leaves when the seed germinates
86
C9) where are the vascular bundles in the stem of herbaceous dicot
The vascular bundles are around the edges to give strength and support
87
C9) where are the vascular bundles in the roots of herbaceous dicot
Vascular bundles are in the middle they help the plant withstand the tugging strains that result from the stems and leaves being blown in the wind
88
C9) where is the vascular bundle in the leaves
In the middle of the leaf. Helps support the structure of the leaf
Branching veins spread through the leaf functioning both in transport and support
89
C9) What are the structures and functions of the xylem
Largely nonliving tissue that has two main functions in a plant-the transport of water and mineral ions and support
The flow of materials is up from the roots to the shoots and leaves in the xylem
Xylem vessels are the main structures, they are long, hollow structures made by several columns of cells fusing together end to end
Thick walled xylem Paraenchyma packs around the xylem muscles, storing food and containing tannin
tannin protects plant tissue from attack by herbivores
Lignified secondary wall that provide extra mechanical strength but do not transport water. Can be laid down in the walls of xylem vessel in several ways. Can have loads of unlignified areas called bordered pits
90
C9) what are the structures and functions of the phloem
Living tissue that transports food in the form of organic solid around the plant from the leaves where they are made by photosynthesis. Phloem supplies cells with sugars and amino acids needed for cellular respiration. Flow of materials in the phloem can go up and down the plant
Main transporting vessels of the phloem are the sieve tube elements. Made up of many cells joined end to end to form a long hollow structure, not lignified
Areas between the cells, the walls become perforated to form sieve plates allowing flow and contents to flow through. The tonoplast, The nucleus and some of the other organelles breakdown. Phloem becomes a tube filled with phloem sap
Linked to the sieve tube elements are companion cells, which form with them. The cells are linked to the sieve tube elements by many plasmodesmata-microscopic channels through the cellular cell wall linking the cytoplasm of adjacent cells. They maintain the sieve tube elements nucleus and all their organelles
The companion cells are very active cells and it is thought that they function as a life-support system for the sieve tube cells which have lost most of their natural cell functions
91
C9) What is the importance of water for plants
Turgor pressure because of osmosis in plant provides a hydrostatic skeleton to support the stems and leaves
Turgor pressure also drives cell expansion - it is the force that enabled plant roots to force their way through tarmac and concrete
Loss of water by evaporation helps to keep plants cool
Mineral ions and the products of photosynthesis are transported in aqueous Solutions
Water is a raw material for photosynthesis
92
C9) what are the adaptations of root hairs as an exchange surface
There microscopic size means they can penetrate easily between soil particles
Each microscopic hair has a large surface area to volume ratio and there are thousands on each growing root tips
Each hair has a thin surface layer through which diffusion and osmosis can take place quickly
Concentration of solutions in the cytoplasm of root hair cells maintains a water potential gradient between the soil water and the cell
93
C9) what are the root hair cells
Root hair cells are the exchange surfaces in plants where water is taken into the body of the plant from the soil
have a root hair is a long, send what what extension from a root hair cell
94
C9) how does water move into the root hair cells
Which soil water has a very low concentration of dissolved minerals so it has a very high water potential
The cytoplasm and vacuolar sap of the root hair cell contains many different solvents, so the water potential is lower
so water moves into the root hair cell by osmosis
95
C9) what are the different ways water moves across the roots to the Xylem
The symplast pathway
The apoplast pathway
96
C9) what is the symplast pathway for the movement of water to the xylem
water moves through the symplast, continuous cytoplasm of the living plant cells that is connected through the plasmodesmata, by osmosis.
The root hair cell has a higher water potential than the next cell along, as a result of water moving from the soil and diluting the cytoplasm.
Water moves from the root hair cell into the next cell by osmosis until reaching the Xylem.
As water leaves the root hair cell by osmosis the water potential of the cytoplasm falls again , therefore maintaining a steep water potential gradient for the movement of water from the soil
97
C9) what is the apoplast pathway for the movement of water to the xylem
Movement of water through the apoplast - The cell walls and the intercellular spaces.
Water feels the spaces between the loose open network of fibres in the cellular cell wall
As water molecules move into the xylem, More water molecules are poured through the apoplast behind them due to the cohesive force between the water molecules
The pull from water moving into the xylem and up the plant along with cohesive forces between water molecules create attention that means there is continuous flow of water through the open structures of the cellulose wall with little resistance
98
C9) how does water move into the xylem
Water moves across the roots in apoplast and symplast pathway until it reaches the end the dermis, the layer of cells surrounding the vascular tissue of the roots
The endodermis is particularly noticeable in the roots because of the effects of the Casperian strip, waxy material called suberin that runs around each of the endodermal cells forming waterproof layers. Water in the apoplast pathway can go no further and is forced into the cytoplasm of the cell joining the water in the symplast pathway
The diversion to the cytoplasm is important as water must pass through the selectively permeable cell surface membrane, this excludes any potential toxic solutes in the soil water from reaching living tissue as the membrane would not have the carrier protein to admit them
The solute concentration of the cytoplasm of the endodermal cells is relatively dilute compared to the cells of the xylem, in addition it appears the endodermal cells actively transport mineral ions into the xylem, as a result the water potential of the xylem cells is much lower than the water potential of the endodermal cells. Increasing the rate of water moving into the xylem by osmosis down a water potential gradient from the endodermis through the sympathic pathway
99
C9) what happens to water once it is inside the vascular bundle
Water returns to the apoplast pathway to enter the xylem itself and move up the plant.
The active pumping of minerals into the xylem to produce movement of water by osmosis results in root pressure and is independent of any other effects of transpiration
Root pressure gives water a push up the xylem but under most circumstances it is not the major factor in the movement of water from the roots to the leaves
100
C9) what are the evidence for the role of active transport moving water from the root endodermis to the xylem
Root pressure increases with a rise in temperature and falls with a fall in temperature suggesting chemical reactions are involved
If levels of oxygen or respiration substrates fall root pressure falls
Xylem sap may exude from the cut end of stems at certain times
Some poisons affect the mitochondria and prevent the production of ATP. Therefore the root pressure disappears
101
C9) what is the process of transpiration
Leaves have a very large surface area for capturing sunlight and carrying out photosynthesis. Their surfaces are covered with a Waxy cuticle that makes them waterproof, important adaptation that prevents the leaf cells losing water rapidly and constantly by evaporation from their surface
When the stomata are opened to allow an exchange of carbon dioxide and oxygen between the air inside the leaf and the external air, water vapour also moved out by diffusion and is lost
This loss of water vapour from the leaves and stems of plants is called transpiration, an inevitable consequence of gases exchange
102
C9) what is the stomata
Important that gases can move into and out of the air spaces of the leaf so that photosynthesis is possible. Carbon dioxide moves from the air into the leaf and oxygen moves out of the leaves by diffusion down concentration gradient through pores in the leaves called stomata.
The stomata can be opened and closed by Guard cells which surround the stmatal opening
103
C9) how does the stomata control the amount of water loss
Stomata open and close to control the amount of water loss by a plant, during the day a plant needs to take in carbon dioxide for photosynthesis and at night when no oxygen is being produced by photosynthesis it need to take in oxygen for cellular respiration.So some stomata need to be open all the time
104
C9) what is the transpiration stream
water moves by osmosis across membranes and by diffusion in the apoplast pathway from the xylem through the cells of the leaf where it evaporates from the freely permeable cellular cell wall of the mesophyll cells in the leaves into the air spaces
The water vapour then moves into the external air through the stomata along a diffusion gradient
Transpiration stream moves the water up from the roots of a plant to the highest leaves
105
C9) how does the transpiration stream work
Water molecules evaporate from the surface of mesophyll cells into the air spaces in the leaf and move out of the stone matter into the surrounding area by diffusion down a concentration gradient
The loss of water by evaporation from a mesophyll cell lowers the water potential of the cell, So water moves into the cell from an adjacent cell by osmosis, along both apoplast and symplast pathways
Repeated across the leaf to the xylem water moves out of the xylem by osmosis into the cells of the leaf
Water molecules form hydrogen bonds with the carbohydrates in the walls of the narrow xylem vessels-adhesion. Water molecules also form hydrogen bonds with each other and so tend to stick together –cohesion. The combination effects of adhesion and cohesion results in water exhibiting capillary action, the process by which water can rise up in narrow tube again The force of gravity.
Water is drawn up the xylem in a continuous stream to replace the water lost by evaporation - transpiration pull
Transpiration pool results in a tension in the xylem, which in turn helps to move water across the roots from the soil
106
C9) what is the name of the model of moving water continuously up the xylem and across the leaf known as
Cohesion tension theory
107
C9) what are the evidence to suggest cohesion tension theory
Changes in the diameter of trees – when transformation is at its height during the day, the tension in the xylem issue is at its highest too. As a result the tree shrinks in diameter. At night, when transpiration is at its lowest, the tension in the xylem vessels is at its lowest and the diameter of the tree increases
When a xylem vessel is broken in most circumstances air is drawn in to the xylem rather than water leaking out
If a xylem vessel is broken and air is pulled in as described, the plant can no longer move water up the stem as the continuous stream water molecules held together by cohesive forces has been broken
108
C9) How does the stomata control the rate of transpiration
Is a turgor driven process
When turgor is lower the asymmetric configuration of the guard cell walls close the pores. When water become scarce, hormone signals from the roots can trigger turgor loss from the guard cells which close the stomata pore to conserve water
When the environmental conditions are favourable the guard cells Pump in solutes by active transport increasing the turgor. Celulose hoops prevent the cells from swelling in the width so they extend lengthways. Because the inner wall of the guard cell is less flexible than the outer wall the cell becomes been shaped and open the pores
109
C9) What does the factors that affect water loss act upon
Any factor affecting the rate of water loss from the leaves of a plant will affect the rate of transpiration
They must either act on the opening/closing of the stomata
The rate of evaporation from the surface of the Leaf cells
The diffusion gradient between the air spaces in the leaves and the air surrounding the leaf
110
C9) how does light affect rate of transpiration
Is required for photosynthesis and in the light the stomata open for the gas exchange needed. In the dark most of the stomata will close.
Increasing light intensity gives increasing numbers of open stomata, Increasing the rate of water vapour diffusing out and therefore increasing the evaporation from the surface of the leaf
111
C9) how does humidity affect the rate of transpiration
The amount of water vapour in the air compared to the total volume of water the air can hold
A very high relative humidity for lower the rate of transpiration because of the reduced of the water vapour potential gradient between the inside of the leaf and the outside air
Very dry air has the opposite effect and increases the rate of transpiration
112
C9) what are the two ways temperature can affect the rate of transpiration
An increase in temperature increases the kinetic energy of the water molecules and therefore increases the rate of evaporation from the spongy mesophyll cells into the air spaces of the leaf
An increase in temperature increases the concentration of water vapour that the external air can hold before it becomes saturated (so decreases its relative humidity and its water potential)
Both factors increase the diffusion gradient between the air inside and outside the plant, therefore increasing the rate of transpiration
113
C9) how does a movement affect the rate of transpiration
Each leaf has a layer of still air around it trapped, by the shape of the leaf and features such as hairs on the surface of the leaves decrease air movement close to the leaf
The water vapour that diffuses out of the leaf accumulates here and so the water vapour potential around the stomata increases intern reducing the diffusion gradient
Anything that increases the diffusion gradient will increase the rate of transpiration. So any movement or wind will increase the rate of transpiration and conversely a long period of steel air will reduce transpiration
114
C9) how does soil water availability affect the rate of transpiration
The amount of water available in the soil can affect transpiration rates
If it is very dry the plant will be under water stress and the rate of transpiration will be reduced
115
C9) what is translocation
Plants transport organic compounds in the phloem from source to sink in a process called translocation
In many plants translocation is an active process that requires energy to take place and substances can be transported up and down the plant
116
C9) what are assimilates
The products of photosynthesis that are transported
Although glucose is made in the process of photosynthesis, the main Assimilates transported around the plant is sucrose
117
C9)What are the main sources of assimilates in a plant
Green leaves and green stems
Storage organs such as tuba and tap root that are unloading their stores at the beginning of a growth period
Food storage in seeds when they germinate
118
C9) what are the main sinks in a plant
Roots that are growing and or actively absorbing mineral ions
Meristem that are actively dividing
Any part of the plant that are laying down food stores, such as developing seeds, fruits or storage organs
119
C9) how is the phloem loaded using apoplast route
In Many plant species sucrose from the source travels through the cell walls and inter cellular spaces to the companion cells and sieve elements by diffusion down a concentration gradient maintained by the removal of sucrose into the phloem vessel
In the companion cells sucrose has moved into the cytoplasm across the cell membrane in an active process.
Hydrogen ions are actively pumped out of the companion cell into the surrounding tissue using ATP. The hydrogen ions return to the companion cell down a concentration gradient via a co-transport protein, sucrose is the molecule that is co-transported
This increases the sucrose concentration in the companion cells and in the sieve element through the many plasmadesmata between the two linked cells
As a result of the buildup of sucrose in the companion cell and sieve tube element, water also moves in by osmosis. Leading to a buildup of turgor pressure due to the rigid cell walls.The water carrying The assimilates moves into the tubes of the sieve element, reducing the pressure in the companion cell and moves up or down the plant by mass flow to areas of lower pressure.
120
C9) how is the phloem unloaded
The sucrose is unloaded from the phloem at any point into the cell that need it
Phloem unloading seems to be by diffusion of the sucrose from the phloem into the surrounding cells
The sucrose rapidly moves on into other cells by diffusion or is converted into other substances so that a concentration gradient of sucrose is maintained between the contents of the phloem and the surrounding cells
The loss of the solutes from the phloem lead to a rise in the water potential of the phloem. Water moves out into the surrounding cells by osmosis. Some of the water that carried the solutes to the sink is drawn into the transpiration stream in the xylem
121
C9) What are the main evidence to show for the principle of translocation
Advances in microscope he allows us to see the adaptations of the companion cell for active transport
If the mitochondria of the companion cells are poisoned, translocation stops
The flow of sugar in the phloem is about 10,000 times faster than it would be by diffusion alone, suggesting a an active process is driving the mass flow
122
C9) What are some questions that remain about the principle of translocation
Not all solutes in the flow and move at the same rate
Sucrose always seems to move at the same rate regardless of the concentration of the sink
No one has yet completely sure about the role of the sueve plate in the process
123
C9) what are xerophytes
In hot conditions particularly hot, dry and breezy conditions – and the water will evaporate from the leaves surface very rapidly. Plants in dry habits have evolved a wide range of adaptations that enable them to Live and reproduce in places where water availability is very low
Many plants that survive in very cold and icy conditions are also Xerophytes- The water in the ground is not freely available for them because it is frozen
124
C9) What are some adaptations of extra Xerophytes
Sunken stomata-many have their stomata located in pits, which reduce air movement, producing A micro climate of still humid air that reduces the water vapour potential gradient and so reduces transpiration
Reduced number of stomata- Have a reduced number of stomata which reduce their water loss by transpiration but also reduce the gases exchange capability
Hairy leaves- have very hairy leaves that create a microcontrol of still humid air reducing the water vapour potential gradient and minimising the loss of water by transpiration from the surface of the leaf
Leaf loss-some plants prevent water loss through the leaves by simply losing their leaves when water is not available. The trunk and branches turned green and photosynthesises with a minimal water loss to keep it alive
Curved leaves -greatly reduces water loss by transpiration, is the growth of carled or rolled leaves. Confining all of the stomata within a micro environment of still humid air to reduce diffusion of water vapour from the stomata
Root adaptations -Long tip roots growing deep into the ground can penetrate several metres, so they can access water that is a long way below the surface.
A mass of widespread, shallow roots with a large surface area able to absorb any available water before a rain shower
125
C9) what is a hydrophyte
Plants that live in water, need special adaptations to cope with growing in water or in permanently saturated swim
Important in surface water plants that the leaves float so they are near the surface of the water to get the light needed for photosynthesis
Waterlogging is a major problem for all hydrophyte. The airspace of the plant need to be full of air, not water, for the plant to survive
126
C9) What are some adaptations of hydrophytes
Very thin or no waxy cuticle- hydrophyte do not need to conserve water as there is always plenty available, so water loss by transpiration is not an issue
Reduce structure to the plant- the water support the leaves and flowersSo there is no need for strong supporting structures
Wide, flat leaves-some hydrophyte have wide flat leaves that spread across the surface of the water to capture as much light as possible
Small roots-water can diffuse directly into stem and leaf tissue so there is less need to uptake by roots
Large surface area stems and roots on the water –this maximises the area of photosynthesis and the oxygen to diffuse into submerged plants
Air sacs -some hydrophyte have air sacks to enable the leaves to float to the surface of the water
